Method and device to sustain a cut flower and its blossoms

ABSTRACT

A plant stem is sealed aseptically by an initially imperforate, stem-penetrable elastomer which is sufficiently flowable and has sufficient self-affinity to form a seal against the stem which is sufficient to resist the flow of liquid around the stem at a pressure of about 0.9 to about 1.2 psi, and an elastomer is provided containing dispersed, suspended particles of a water-insoluble, hydroscopic polymer.

This application is a continuation-in-part and divisional of applicationSer. No. 07/383,238 filed July 19, 1989.

FIELD OF THE INVENTION

This invention relates generally to the field of elastomers, and moreparticularly to an elastomer useful in a method of preserving the lifeof a cut plant or flower.

BACKGROUND AND SUMMARY OF THE INVENTION

It is a common practice to sustain the life of cut plants such asflowers by means of inserting a basal end of the plant stem in areservoir containing a liquid such as water, or a nutrient liquid. Sucha method provides some increase in the life of a plant or flower, butfor many varietals the flower lasts but one or two days prior to theonset of wilting even when the cut stem of the flower is immersed in aliquid-containing reservoir such as a vase. It should be understood thatthe term liquid as used herein is meant to include water, a watersolution containing plant nutrients, or any other solution in which aplant stem is immersed to sustain the plant.

Accordingly, it has been a desideratum to develop a method or device forincreasing the life of flowers or other plants which are cut from theirnatural state. For example, U.S. Pat. No. 3,842,539 discloses a devicewhich inhibits the flow of water to a stem of a cut flower, and containsion exchange resin to remove harmful ions from the water. The methodinvolves the placing of the basal end of the flower stem in a conduit ortube, and the water enters the basal end of the stem only after passagethrough the resin mass. U.S. Pat. No. 4,103,457 discloses a totallyenclosed nutrient liquid supply system including a pouch, tubing andlatex sleeve around the stem of the flower, with pressure on the pouchfeeding liquid to the stem. The enclosure of the liquid supply system issaid to inhibit contamination of the nutrient liquid during protractedperiods. The disclosures of U.S. Pat. Nos. 3,842,539 and 4,103,457 areboth incorporated herein by reference.

While these two patents have attempted to preserve the life of cutflowers, the methods are significantly complex and costly, and even sofail to provide a practical or successful method or device forpreserving the life of a cut plant or flower.

The present invention provides a novel system for providing liquid to acut plant wherein substantially all the liquid required by the plant ispresented to a basal end of the plant stem only after passage through anapparatus which includes a filtration means having a porosity which issufficient to permit liquid to pass from the reservoir to the stem, butinsufficient to permit the passage of microorganisms with the liquid.

In a preferred embodiment, all liquid required by the plant passesthrough a porous membrane having a porosity which is insufficient topass microorganisms. As used herein, the term microorganism is meant toinclude all organisms such as bacteria, fungi and viruses which areharmful to plant survival (i.e., pathogenic organisms) or microscopic orsubmicroscopic organisms which grow on a nutrient substrate such asplant tissue. While I do not wish to be bound to any particular theory,it appears that plant wilting, when the cut stem of a plant is immersedin a nutrient liquid or water, is due primarily to the growth of suchmicroorganisms on the exposed xylem tissue of the cut stem, which blocksthe flow of liquid into the xylem tissue or, in the case of pathogenicmicroorganisms, may tend to poison the plant. When the plant's vascularsystem is thus blocked, the negative pressure on the vascular systemfrom transpiration from the plant leaves causes cavitation, whichresults in the collapse of the vascular system and wilting of the plant.

Broadly, one aspect of the invention comprises providing a conduit ortube having an end adapted to receive a basal end of the plant stem, andincluding a means to seal a stem receiving portion of the apparatus andthe basal end therewithin from the influx of microorganisms whilepermitting the transport of water or a nutrient medium. Preferably, thisstem receiving portion of the apparatus is sterilized prior to use toassist in maintaining the basal end of the isolated from microorganisms.

A portion of the conduit is adapted to be exposed to the liquid in thereservoir. A filtration means such as a membrane or a filtering portionof the apparatus is disposed between the stem receiving portion and theliquid in the reservoir in a manner such that all liquid which passes tothe plant from the reservoir must flow through this filtration means,having a porosity which is insufficient to permit the passage ofmicroorganisms, so that the described blockage of the liquid flow isavoided.

Generally, a filter having an effective porosity of less than 3 microns,preferably from about 0.05 to about 0.45 microns, is sufficient topermit the passage of liquid such as water to the stem, but insufficientto permit the passage of deleterious microorganisms with the liquid.Most preferably, a filter having an effective porosity of about 0.2microns or less is employed. Effective porosity, as used herein, isdefined as the ability of the filter to resist the transfer of particlesof the specified size.

The hydrophilic filters of the invention, that is, filters which passliquid but are capable of excluding the passage of microorganisms to thestem, also serve to inhibit the passage of air bubbles (emboli) whichmight otherwise enter and "air-lock" the plant's vascular system,blocking the uptake of liquid and contributing to wilting, whilepermitting the passage of dissolved gases necessary for sustaining theplant.

As shown in the embodiments described herein, the filtration means maybe a planar film having the appropriate porosity, or may comprise aporous mesh-like or woven polymer which acts as a depth filter, that is,a polymer which has an effective porosity sufficiently small to resistthe passage of microorganisms even though the actual porosity of a thinlayer of the material is larger than the required amount. The filtrationmeans may also be a hollow fiber having a lumen with a diameter which issufficient to permit the fiber to wick the fluid from the reservoir tothe stem, if no liquid pressure is applied, and a wall porosity which issufficient to permit the transport of liquid but insufficient to permitthe passage of microorganisms with the liquid.

The hollow fiber may have a wall porosity of less than 3 microns,preferably from about 0.05 to about 0.45 microns, and most preferablyhaving a porosity defined by having pores of less than about 0.2 micronsdiameter. Such fibers may be made, as is known in the art, from ahydrophilic resinous material. Since the basal end of the plant stem issealed within a first portion of the conduit, flow through thisfiltration means is the only source of liquid for the plant and theplant accordingly receives fluid from the reservoir in the absence ofdeleterious microorganisms.

In another aspect of the invention, the sterile conduit portion includesa bactericidal means disposed to be adjacent the stem to further protectthe cut end of the stem from the influx of microorganisms whichcontribute to vascular blockage.

Another contributing cause of wilting in cut flowers and plants isimproper liquid pressure on the plant's vascular system. The transportof water in a natural plant is the result of a combination of "pull"from the evaporation of water from the leaves and "push" from pressurecreated by the roots. When a plant is harvested the positive pressure onthe vascular system from the roots is removed, and if the plant stem isof sufficient height it appears that cavitation will occur, that is, theformation and collapse of regions of low pressure, and massive tissuedamage ensues which promotes the death of the cutting.

According to another aspect of the invention, significant additionaladvantages with respect to longer stemmed plants are provided by the useof a pressure system which produces a pressure of from about 0.9 toabout 1.2 psi to the liquid at the cut end of the plant stem. Broadly, amethod for preserving a plant having a stem, wherein the stem issupplied from a liquid source with a liquid is provided which includesplacing a basal end of the stem in an apparatus having a conduit withsealing means disposed around the stem which seal the conduit portionand the basal end therewithin against the influx of microorganisms, andproviding a pressure of from about 0.9 to about 1.2 psi on the liquid atcut end of the stem. Preferably, the liquid in the liquid source issterile.

Significant advantages result from the combination of the filtrationdevice and the pressure system. Preferably, a device for the display ofa plant having a stem with a basal portion including a cut end isprovided which comprises a first portion adapted to contain liquid; asecond portion defining an area adapted to receive the cut end of thestem, and to receive liquid from the first portion; and a sealing meanson the second portion, adapted to enclose the basal portion of the stemand seal the stem against the egress of liquid from the device. Thedisplay device also includes a filter having a porosity of from about0.05 to about 0.45 microns disposed between the first and the secondportions and disposed to seal the second portion from the first portionin a manner such that microorganisms cannot flow from the first to thesecond portion, and means for providing a pressure of from about 0.9 toabout 1.2 psi on the liquid at cut end of the stem.

Since long stemmed plants also benefit from a positive pressure systemduring transport, a novel method for the transport of plants is providedwherein the filtration device of the invention is filled with water andattached to the cut end of the plant, and the plant is then positionedwith the leaves or flower lower than the cut stem, so that the combinedstem and device act as a water column to provide sufficient pressure toovercome the tendency of the vascular system to cavitate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a filtration and stem support deviceuseful in increasing the life of a cut flower in water, shown inposition attached to the basal end of the stem;

FIG. 2 is an enlarged, cross-sectional side view of a similar deviceinstalled on a plant stem and immersed in water;

FIGS. 3 and 4 are cross-sectional side views of alternative devices ofthe type shown in FIGS. 1 and 2;

FIG. 5 is a cross-sectional side view of an additional embodiment of thefiltration device;

FIG. 6 is a cross-sectional side view of yet another embodiment of thefiltration device;

FIG. 7 is a cross-sectional side view of still another embodiment of thefiltration and support device;

FIG. 8 is a side view, partially in cross-section, of a reservoirassembly for use with a filtration and support device such as is shownin FIG. 7; and

FIG. 9 is a sectional side view of another stem support and sealingdevice of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is seen a unitary, i.e., one-piece, device 10for increasing the life of a cut flower 12. This device 10, as seen indetail in FIGS. 2, 3 and 4, includes a conduit or tube 14 which receivesa stem 16 of the flower 12. Specifically, a basal end 18 of the stem 16is received in a first conduit portion 20, and a second conduit portion22 of the conduit 14 is adapted to be disposed in a reservoir of wateror other liquid such as a nutrient solution.

Turning now to FIG. 2, the device 10 is seen to include, in thisembodiment, a casing 30 made of solid, resinous material commonlyreferred to as plastic. A stiff, resilient rubber-like material isparticularly advantageous. The basal end 18 of the stem 16 is seen to beincluded in the first portion 20, and sealed against the influx ofliquid and microorganisms by a sealing means 32 which is seen to beconstructed of a flexible, resilient material such as latex or the likewhich tightly encircles the stem 16 as well as the outer wall 34 of theconduit 14 surrounding the first portion 20.

In this regard, ridges 36 and 38 may be formed in the wall 24 to assistin the sealing of the latex means 32 against the wall 34 and to providepositioning ridges so that the resilient seal 32 may be rolled orconvoluted downwardly around the walls of the first portion 20 forinsertion of the basal end 18 of the stem. This is described in moredetail with respect to FIG. 3. The resilient means 32 may be retained onthe walls of the first portion 20 by the elastic pressure inherent insuch resilient material, or may be adhesively attached thereto.

The first portion 20 is seen to be sealed and isolated against the flowof microorganisms along with the liquid from the second portion 22 by asecond sealing means 40 which is seen to be formed above a platform 42disposed between the first portion 20 and the second portion 22 of theconduit 14. The sealing means 40 may be formed from a wide variety ofpolymers, preferably a non-hydrophilic, high-viscosity polymer such assilicone or polyurethane which is compatible with and non-toxic to theflower, and which is non-invasive with respect to the porosity of thefiber walls.

The flow of liquid from the second portion 22 to the flower is providedsolely by a filtration means comprising a hollow fiber 44. This fiber ispreferably formed from a hydrophilic material and has a lumen which willpermit the flower to wick fluid through the fiber and a wall porositywhich will permit the passage of water through the fiber wall at aquantity sufficient to inhibit wilting of the flower, yet a porositywhich is insufficient to permit the passage of microorganisms throughthe fiber wall.

The hollow fiber 44 has a lumen diameter of up to about 400 microns,preferably up to about 120 microns, and transverse channels whichprovide a porosity of from about 0.01 to 0.45 microns, preferably lessthan about 0.2 microns. The fibers are preferably made from ahydrophilic resinous material such as cellulose nitrate and/or celluloseacetate, and the hydrophilic porosity provided by the channels which areformed in the fiber wall permits the influx of liquid, which is thentransported by capillary action to the natural xylem tissue contained inthe basal end 18 of the flower. The channels and fibers employed aredescribed and shown in some detail in FIG. 10 of application Ser. No.07/050,262, filed May 14, 1987, which is specifically incorporatedherein by reference. A preferred fiber is that manufactured by MicrogonCompany of Laguna Hills, Calif., and identified by the designationCHF-96B-263 having a nominal pore size of 0.1 microns. Since the hollowfiber filtration means inhibits the passage of microorganisms, and sincethe wicking action of the flower can draw fluid only through thisfiltration means, the flow of liquid into the basal end of the stem 18cannot be blocked by the growth of organisms across the natural xylemtissue of the flower.

The upper ends 46 of the looped fiber 44 are seen to be adjacent, orabut, the natural xylem tissue of the flower. While one such hollowfiber is sufficient to pass sufficient liquid (150 ml/day) to sustain aflower such as a rose, additional looped fibers may be included. Singlefibers may also be used as long as the lumen disposed in the secondportion 22, that is, the end of the fiber exposed to the liquid in thereservoir, is closed. The upper end 46 of the fiber, that is, the end inthe sterile first portion 20 of the device 10, may be open or closeddependant on the porosity of the fiber. Preferably, the end of the fiberin the sterile portion is open to facilitate solution flow.

As shown in FIG. 2, the liquid from the reservoir, that is, the liquidsource, enters the second portion 22 to be in liquid communication withthe fiber 44 through a plurality of openings 48. As shown, at least oneof the openings 48 is preferably positioned at the top of the secondportion 22 so that air is not trapped when the device is submerged in aliquid in a manner which inhibits the wicking through the fiber. Inpractice, the liquid level will be higher on the plant stem than isshown in FIG. 2, and it will be apparent that the entire device 10 willbe significantly submerged in water when a flower with the deviceattached is placed in a vase. Even though this submersion will causesome hydraulic pressure to be exerted on the device, the water or liquiddrawn through the membrane is still drawn by the plant essentially bywicking force or capillary action.

Alternative embodiments are shown in FIGS. 3 and 4. In FIG. 3, theconduit 14 of a device 49 is seen to be in the form of a tubular rigidplastic conduit having a rigid annular edge wall and an intermediateplatform 52 between the first portion 20 and the second portion 22. Thisplatform 52 is seen to include perforations 54 which permit the influxof liquid from the second portion 22 to a filtration means which is seento comprise a membrane 56 which is formed from a capillary-pore membranesuch as those sold by the Nuclepore Corporation. These membranes arepolycarbonate and/or polyester films, or laminates of such polymers,which are exposed to sufficient gamma or other radiation, or othermeans, to form a perforate surface having a porosity defined by poreshaving a diameter of up to about 0.45 microns, preferably up to about0.2 microns. A nuclepore or similar film having a porosity of thisamount will serve as a membrane filtration means sufficient to permitthe wicking of liquid from the reservoir to the stem, but this porosityis insufficient to permit the passage of microorganisms with the liquid.

The membrane 56 is sealed at the edges adjacent the edge wall 50, by asealing means such as a biocompatible silicon rubber so that the flowfrom the second portion 22 to the first portion 20 can take place onlythrough the described pores. The resilient sealing means 32 in FIG. 3 isseen to be convoluted or rolled down around the wall 50 of the firstportion 20, and retained by a ridge 36, to facilitate the insertion ofthe basal end of the stem of the flower (not specifically shown). Afterinsertion of the stem into the first portion 20, the convoluted sealingmeans 32 is then rolled upwardly to tightly seal the stem against theinflux of fluid. This tight seal against the stem is desired due to thefact that the entire device may be submerged in the liquid in thereservoir or vase.

Any of the sealing means described herein may also be molded orotherwise formed with a graduated or tapered inner diameter so that avariety of stem diameters may be received. Strain on the Krayton orHytrel (DuPont) material may be minimized by molding a cap to fit overthe upper end of the conduit, the cap having a tubular member extendingtherefrom to form the seal around the stem. It should be understood thatthe tubular stem sealing means can extend inwardly or outwardly from thestem receiving conduit, and that a plurality of stem receiving tubes canadvantageously be positioned on one such molded cap.

Another alternative device 60 is shown in FIG. 4. In this embodiment,the entire conduit 14 is formed from a resilient tube, for example,latex, which receives the basal end 18 of the stem in the tight, sealingarrangement described above. In this embodiment, a sealing means 40seals the first portion 20 from the second portion 22, and the loopedfiber 44 courses from a porous mass 62 through the sealing means 40 tothe second portion 22 and thereafter back through the sealing means tothe porous mass 62. The porous mass may be formed from any sponge orsponge-like means that will draw liquid by capillary action, such as aporous urethane polymer. This sponge 62 wicks fluid from the upper endsof the fiber 44 to the natural xylem tissue of the stem 18. In certainuses or for certain varietals, the sponge means 62 provides significantadvantages.

It should be understood that the invention comprises maintaining thestem of the plant in contact with the liquid under conditions such thatthe liquid is presented to the stem only after passage through thefiltration means described herein. Any of the specific filtration meansmay be interchanged in the embodiments shown in FIGS. 2, 3 and 4, and,for example, the sponge means 62 may be employed with any of thedescribed filtration devices.

Prior to the insertion of the plant or stem into the sterile portion ofany of the devices described herein, the inserted portion may be firstcleaned or dipped in a non-phytotoxic bactericide solution so that thestem receiving portion is maintained free of microorganisms. Inaddition, an internal bactericidal member within the sterile portion,such as is shown in FIG. 5, provides significant advantages.

In FIG. 5, a device 68 comprises a first or upper portion 70 and asecond or lower portion 72, both portions being cylindrical and shown incross-section in the Figure. The upper portion 70 has an uppercylindrical member 74 and a lower, inverted cup-like member 76. Thelower portion 72 has a lower, essentially cylindrical member 78 and anupper cup-like member 80 which closely mates with the lower cup-likemember 76 in a snap-fit relationship so that the portions 70 and 72 canbe retained in the cooperating relationship shown. The lower portion 72has lateral openings 82 and, if desired, a bottom opening 84 to permitthe influx of water or liquid into the member 78. The portion 72 alsoincludes a sponge 86, in the cup member 80, which is in fluidcommunication with a filtration means which comprises a hollow fiber 88,such as those described above. The sponge 86 may be impregnated with abactericidal agent, such as is discussed with respect to the sponge 90shown in FIG. 5. One end of the fiber 88 is seen to be received in thesponge, the fiber then looping into the liquid receiving portion 78 ofthe device, with the other end of the fiber then returning to bereceived in the sponge.

The upper cylindrical member 74 receives a hollow cylindrical sponge 90,which includes a portion 92 which extends above the top of the member 74to form a closed apex. This sponge contains a bactericidal agent andserves as a stem disinfecting means. For example, the sponge may besoaked in a 0.03% solution of 8-hydroxy-quinoline citrate prior toinsertion into the member 74. A sponge which is complexed with moleculariodine, known in the art, is particularly advantageous in thedissolution of the iodine is limited while retaining the bactericidaleffect.

The upper portion 70 and part of the lower portion 72 is encapsulated ina resilient coating 100 which extends from the apex of the upper spongepart 92, along the sides and inverted cup portion of the upper portion70, and into an upper part 102 of the lower portion 72. The coating 100embeds the fiber 88 in place, and creates a closed space 104 within theupper portion 70, including the sponges 86 and 90 and the tips of thefiber 88, which may be sterilized and maintain such sterility againstthe influx of microorganisms due to the inhibitory porosity of the fiber88.

This coating, like the potting material which forms the sealing means 40referred to above, should be non-phytotoxic, and non-invasive as to thepores or porosity of the fiber so that the lumen of the fiber and theflow of liquid is not inhibited. In this embodiment, the coating ispreferably a vinyl polymer known as plastisol. Specifically, a plastisolmanufactured by the Goray Co. of Anaheim, Calif. and sold under thedesignation RFB-27-1 has been found to be particularly satisfactory.

The device 68 shown in FIG. 5 is assembled by first inserting the endsof the fiber into a slot in the sponge 86, and placing the sponge andfiber so that the lower end of the fiber extends into the lower portion72. The sponge 90, impregnated with a bacteriocidal agent, is theninserted into the upper portion 70 and the two portions are assembledinto the mating relationship shown. The sponge 86 is seen to be heldfirmly against the cup member 80 by the cup member 76. The device 68 isthen inverted, and dipped into a heated plastisol to a level sufficientfor the plastisol to flow into the lateral openings 82 and seal thefiber and sponge 86 to the lower portion 72. Preferably, the sponges 86and 90 are wetted prior to assembly, and after assembly the device issterilized with gamma radiation or an electron beam and placed insterile packaging.

In use, the tip of the apex of the coated upper portion 70 is cut off orpunctured by the user, so as to provide an open, resilient tubularmember for the insertion of the stem of the plant or flower onto thespace 104 until the basal end of the stem abuts the sponge 86. Theresilient coating around the apex seals against the stem, and theresilient action of the sponge 90 serves to perform a sterile wipefunction on the stem and to retain the device on the inserted stem. Thedevice and the stem may then be inserted in water, and the xylem tissuein the stem wicks water, free of microorganisms, through the fiber 88sponge 86 where it flows by capillary action to the stem in the sterilespace 104.

In an alternative embodiment, the entire conduit could be formed from aporous plastic material such as the spun, high densitypolyethylene/polypropylene material which is used to form leach pipes orthe tips of ball point pens, and which has an effective porosity whichis insufficient to permit the passage of microorganisms. This conduitcould have a single, upper open end which is closed with plastisol orother sealing medium around the stem such as is described with respectto FIG. 5. This closed, porous conduit would thus constitute a porousmembrane having a porosity which is insufficient to permit the passageof microorganisms with the liquid which is drawn solely by capillaryaction through a membrane to the plant.

In yet another embodiment, FIG. 6 shows a unitary filtration apparatus110 which comprises a tube or conduit 112 which may be formed frompolycarbonate, acrylic or styrene polymers or other appropriatematerial, and which is shown to have an overall length of about one andone-half inches. The conduit 112, for example, has been made from astyrene tube having an outer diameter of 1/2 inch with a wall thicknessof 1/16 inch. A stem sealing means 114, preferably an elastic film suchas latex rubber or preferably the Krayton brand thermoplastic rubbermanufactured by the Shell Chemical Company, is attached to the upper endof the conduit 112. A tube of Krayton D 3402 with a diameter of about3/16 inch and a wall thickness of from 14-40 thousandths of an inch maybe cut to an appropriate length, stretched over the top of the conduit112, and heat sealed or sonic welded at the opposite end to form aclosed apex 116 shown in the drawing. Ridges such as the ridges 36 and38 in FIG. 2 may be included around the upper end of the conduit 112 toassist in the sealing of the film 144 against the conduit.

As will be apparent from the foregoing description, the apex 116 of thesealing means 114 is cut by the user, and the cut basal end of a plantstem inserted into a sterile, inner portion 117 of the conduit 112 withthe cut apex forming a seal around the stem which resists the influx ofmicroorganisms, as does the seal formed by the lower end 118 of the tube114 with the upper end of the conduit 112.

A filtration means is provided at the lower end of the conduit 112 bythe placement of a disc 120 which has a porosity sufficient to permitthe passage of liquid, but insufficient to permit the passage ofmicroorganisms. In this case, a capillary-pore membrane such as thosesold by the Nuclepore Corporation and described above with respect toFIG. 3 is employed. The disc 120 is secured to and sealed against theend of the conduit 112 with a solvent such as ethylene dichloride orother appropriate adhesives.

A porous, protective cap 122 is secured to the lower end of the conduit112 after the attachment of the filtration disc 120, by the use of anadhesive such as FMD Locktite adhesive which is placed between the inneredges 124 of the cap 122 and the side edges 126 of the conduit 112 sothat the flow of liquid through the filter disc 120 is not impeded.Alternatively, the porous cap 122 may be attached to the device by sonicwelding or may be held on by a pressure captivation fit, as may beappropriate. The cap may be made of a variety of materials which areporous and which will protect the disc 120, such as a woven polyesterwhich has sufficient porosity to pass water at a high rate but is yetable to act as a pre-filter to remove large particles which wouldotherwise clog the microorganism filtration means. More particularly,the hydrophilic high density polyethylene porous plastic materialmanufactured by Porex Technologies of Fairburn, Ga., with a nominalporosity of about 30 microns and an effective filtration of down to 4.5microns (acting as a depth filter), has shown significant advantages inthat it has passed water in amounts of 25 ml/day to roses in theapparatus of FIG. 6. It should be understood that if the cap 122 isformed from a material which has a porosity of the type described forthe disc 120, the disc could be omitted and the cap 122 would serve asthe filtration means, i.e., filtration membrane, of the invention.

The apparatus shown in FIG. 6 also includes, as a means for exhaustingair from the inner portion 117 of the apparatus 110, an air permeablebut liquid impermeable portion such as a hydrophobic porous plastic port128 which is secured by adhesive or other means to the upper end of theconduit 112 above the level of the cut end of the stem which is insertedinto the sterile portion or cavity 117. The 10 micron Porex brand porousplastic described above, when employed in a hydrophobic state, will passair but will not permit the passage of microorganism containing liquiddue to the hydrophobic nature of the material. The Porex brand porousplastic material may be purchased in either hydrophobic or hydrophilicform. When a device of the invention containing the air exhausting means128 is inserted into water, the air contained within the sterile stemcontaining cavity is quickly purged from the cavity by water enteringthrough the filtration means so the water level easily rises to theheight of the cut end of the stem.

The device shown in FIG. 6 can be used to illustrate an aspect of theinvention which is particularly advantageous in introducing water or.nutrient liquid into the stem receiving portion of the device ininstances in which the air exhausting plug 128 is not employed. In suchan instance, the filter disc or membrane 120 is impregnated duringassembly with a non-phytotoxic, water soluble substance which willinhibit the passage of air through the membrane. For example, the disc120 may be coated with glycerine which changes the tangent angle of thepores in the membrane to render the membrane impervious to the passageof air up to a pressure of 10 psi.

After the elastic tube 114 is placed over the conduit 112, but beforethe sealing of the upper end of the tube, a vacuum is formed within thecavity 117. In practice, the upper end of the elastic Krayton film 114has been stretched over a one-half inch flexible tube, connected to avacuum pump, which evacuates the cavity 117 pulling the flexible filminto the device. The elastic film was then pulled out of the device, andsonically welded to seal the vacuum, and cut above the sonic weld lineto form the closed apex 116. With the glycerine closing the only inletto the cavity, and since glycerine has a high vapor point and will notevaporate, the vacuum may be maintained for long periods of time.

Immediately prior to use, the filter end of the evacuated device isplaced in water. The water dilutes and removes the viscous coating, andthe vacuum draws sterile water into the device to substantially fill thecavity 117 in less than one minute. When the cavity is filled, the apex116 is cut below the sonic weld and the stem, preferably cut to a 45degree angle, is inserted as described above.

After a device such as the device 110 of FIG. 6 is filled with water andthe stem of the plant is inserted, it may be appropriate to transportthe plant for a short distance prior to placing the plant, e.g., aflower, in a vase. In yet another aspect of the invention, the lower endof the device 110 may be equipped with a removable cap, adapted to sealthe water with the device, which may be removed for the filling of thedevice and then replaced for transport. For example, an additional waterimpermeable cap of a shape similar to the cap 122 may be placed over thelower end of the device. Alternatively, a plastic or coated paper discwith a patterned ring of water resistant adhesive around the outer edgemay be employed to seal the device during transport.

Any of the unitary stem receiving filtering apparatus described abovemay be equipped with a bladder attached to the lower portion of theconduit, for example, and adapted to serve as a temporary reservoir andfeed liquid to the plant during transport. The Krayton or other elasticfilm is particularly adaptable for this purpose, and a tube of suchmaterial may be filled with tap water and stretched over the lower endof the conduit of the apparatus shown in FIG. 6.

The wicking filtration device has been shown to provide significantadvantages in extending and preserving the life of cut flowers. Forexample, a cut Cara-mia rose normally has a life of no more than fivedays, prior to wilting. However, when inserted into the device of theinvention as is described with respect to FIG. 2, with a sponge meanssimilar to the sponge 86 in the first portion 20 beneath the basal endof the stem and in fluid communication with the upper end of the fiber,and inserted in water, both long stem and spray varietals of theCara-mia rose have lasted in excess of 49 days without wilting and thespray varietals have supported continued blossoming of unopened blossomsduring that period. The filtration apparatus of the invention isadaptable to a wide variety of additional plants, in particular,bunch-type crops such as grapes wherein the apparatus is installed onthe primary stem of a bunch after harvest with a transport bladderattached.

As referred to above, a vascular plant is a closed-loop biological pumpwherein water containing microelements is transported from the roots tothe leaves by a combination of "pull" from transpiration and "push" fromthe roots. Since the filtration device described in FIGS. 1-6 depends ontranspiration from the leaves and the wicking of liquid through thefilter, some longer-stemmed plants benefit from a positive pressure atthe basal end of the stem which approximates the root pressure in thenatural plant. Depending upon the particular varietal, plants or flowerswith stems shorter than 7 to 8 inches permit a significant extension ofplant life solely with the above-described filtration device, but longerstemmed varietals may suffer from what is termed "neck droop" afterseveral days. While it is known to apply a distinctly higher pressure toplant cuttings, see, for example, the patent to Carlisle U.S. Pat. No.4,103,457, I have found that the deficiencies suffered from cavitationin plants can be overcome only by the use of a pressure from about 0.9to about 1.2 psi at the end of the stem. At pressures less than 0.9 psi,long stemmed plants cavitate and wilt. At pressures greater than 1.2psi, the plant vascular system is over pressurized and damaged, causingexcessive weeping of water from the bottom side of the leaves.

FIG. 7 shows a filtration device which may be employed either in thewicking filtration system described above in FIGS. 1-6, or in a positivepressure filtration system. In FIG. 7, a filtration device 150 is shownto be comprised of a conduit portion 152 and a stem sealing means 154.The conduit 152 and the means 154 are similar to the conduits andsealing means described above with respect to FIGS. 1-6, and are made ofsimilar materials.

The device 150 also includes an end cap 156, also constructed fromthermoplastic material, which includes an annular outer wall 160 and anannular inner wall 162 which form an annular valley 164 therebetween.The cap 156 also includes a lower ring shaped projection 166, includingan outer, inwardly tapering wall 168. The ring structure 166 forms anopening 170 which permits the flow of liquid through the center portionof the end cap 156.

The lower end of the conduit 152 includes an inwardly projecting annularcollar 172 which joins an internal annulus 174, and forming an opening176 which permits the flow of liquid into a cavity 178 of the conduit152 from the opening 170 in the end cap 156.

A membrane filter 180, having a porosity sufficient to inhibit thepassage of microorganisms as set forth above, and a pre-filter 182 aredisposed between the conduit portion 152 and the end cap 156. When thedevice 150 is assembled, the filter 180 and pre-filter 182 are placedbetween an annular ridge 184 on the top of the inner wall 162, and ashoulder 186 of the annular collar 172. A lower annular bottom portion188 of the conduit 152 is then press-fitted into the valley 164 of theend cap 156 and sonically welded in the valley. Welding lugs 190 arepositioned on the lower edge of the ring 188 to aid in sonic welding. Itshould be understood that RF welding or a suitable adhesive may also beemployed.

When the conduit 152 and end cap 156 are thus secured, the ridge 184forces the filter 180 and pre-filter 182 against the annular shoulder186 with sufficient force to seal the filtering members between therespective abutting parts. This force is sufficient to prevent thepassage of liquid around the filter 180, so that all liquid from theopening 170 must flow through the filter 180 to reach the cavity 178.

As described above with respect to FIG. 6, the prefilter 182 hassufficient porosity (e.g. down to about 10 microns) to remove largeparticles and debris such as microscopic calcium and iron salts whichwould otherwise clog the membrane 180. The internal annulus 174 is seento form an annular void 192 in the cavity 178.

In FIG. 8, a plant or flower display device 200 includes a first portion202 which is adapted to contain liquid in a cavity 204 which is formedbetween a lower wall 206, a back wall 208, a top wall 210 and a curvedfront wall 212. The first portion or reservoir 202 may be constructedfrom thermoplastic resin by a wide variety of molding techniques, andpreferably is formed from 2 or more pieces which are sonic welded oradhesively joined in order to facilitate the molding process. The topwall 210 is shown to include a first opening 214 defined by an annulartapering edge 216, an second opening 218 which is defined by a taperingedge 220.

A second portion 222 of the device 200 is seen in an elevated positionabove the first portion 202. The second portion 202 is the filtrationdevice described in FIG. 7, and accordingly includes a sealing means 224with a sonically-welded apex 226 which may be adapted to enclose thebasal portion of the stem of a plant and seal the stem against theegress of liquid from the filtration device 222. When the stem of theplant is this inserted through the sealing means 224, the cut end of thestem will be understood to be received within the portion 222, in anarea shown in FIG. 7 by the reference numeral 178.

The portion 222 also includes an end cap such as the end cap 156 in FIG.7, and includes an annular inwardly tapering end piece 228, which mateswith the tapering edge 216 in a liquid sealing relationship, and ashoulder 230 which abuts the top wall 210 when the portion 222 isinserted into the portion 202.

The display device 200 also includes means, designated generally by thereference numeral 240, for generating pressure on the liquid in thecavity 204 and thus on the cut end of the stem in the second portion orfiltration device 222. The means 240 comprises a first column portion242, which includes an annular tapered lower edge 244 and a seating ring246 adjacent thereto. The. tapered edge 244 mates with the edge 220 in aliquid-sealing arrangement. The ring 246 provides support for the column242 when mounted by abutting the top wall 210 surrounding the opening218. The column 242 also includes an upper end 248 which includes anannular, internal tapered edge 250.

A second column 252 is also provided, having a lower end which includesa tapered annular edge 254 and a shoulder 256. The tapered edge 254mates in a sealing arrangement with the internal tapered edge 250 in aliquid-sealing fit. The lower shoulder 256 adjacent to the ring 254provides additional sealing and support by resting on the upper end 248of the column 242. The column 252 also includes an additional innertapered upper edge 258 so that additional columns may be stacked toincrease the pressure within the cavity 204.

In use, a flower or plant is inserted into the device 222, as describedabove, by cutting the sealed apex 226. The device 222 is then insertedin a sealed relationship in the opening 214. Thereafter, the column 242is inserted in a sealing relationship in the opening 218 and the cavity204 is filled with water or nutrient solution. Additional columns suchas the column 252 are then added to increase the height of the liquid,preferably to a height approximately equal to the flower or uppermostleaf, that is, the upper end of the stem. As stated above, the optimalpressure for most varietals is from about 0.9 to 1.2 psi. It should beunderstood that the height of the columns, and the pressure produced,will depend largely on the diameter of the column members. Generally, acolumn having an inner diameter of about 1/4 inch and a heightapproximately equal to the length of the stem above the liquid in thecavity 204 has been found to provide significant advantages.

It should be understood that a variety of locking, sealing andattachment devices may be employed with respect to the device 222 andthe column members 242 and 252. For example, interlocking tabs may beprovided on the top wall 210 and the device 222 and column member 242,or threaded fittings may be employed with gaskets if desired. Such meansmay also be employed between the respective collar members. In addition,it may be advantageous to equip the opening 214 with a ball valve orduckbill valve which is opened by the insertion of the tapered end 228so that when the device 222 is removed from the display device 200, theegress of water from the opening 214 due to the pressure in the column240 is inhibited. In addition, it should be understood that a widevariety of shapes and sizes of the display device may be constructed,and a nearly unlimited number of filtration devices 222 may be insertedin a plurality of openings in the reservoir 202. For example, areservoir equipped with a large number of valve-closed openings may beprovided with water pressure from a flexible tube leading to an overheadreservoir, and cut flowers in spearing filtration devices inserted intothe reservoir for display in a flower shop.

Another novel feature of the discovery of the benefits which result fromthe application of the described discovery on the effect of pressure onthe cut end of the flower stem is that a cut flower may be stored ortransported by positioning to plant so that positive pressure on thewater column within the plant stem is increased. The life of a storedflower may be increased by placing inserting the basal end of the plantin a filtration apparatus having a filter means and a portion containingliquid, and placing the plant in a position which causes the watercolumn formed by the vascular system and the liquid in the apparatus tofacilitate the "pull" of water into the vascular system. For example,the plant/apparatus combination may be placed with the stem in aposition so that the distal end (e.g., the flower end of the plant) isdisposed at or below the level of the liquid in the apparatus.Preferably, the desired positive pressure may be created by storing ortransporting the flower in an inverted position with the with the cavityin the filtration device filled with liquid. As used with respect tothis aspect of the invention, the term inverted means to position theflower or leaf end of the plant at the level below the basal end towhich the filtration apparatus is attached.

In FIG. 7, a construction is shown which provides significantadvantages. For example, the filter 180 and/or prefilter 182 of thedevice 150 could be coated with glycerine, as described above, and avacuum formed within the cavity 178. When the flowers are cut in thefield, the evacuated device is inserted in water and the cavity 178fills. The sealing means 154 is then cut and the flower inserted. Theflower is then inverted, so that liquid in the cavity 178 providessufficient pressure to maintain the positive pressure on the flowers inthe flowers vascular system. Since the water in the cavity 178 has beeneffectively sterilized by the filter 180, the vascular system is notblocked by the growth of bacteria. If the inserted stem has significantbacteria or if the stem is not appropriately cleaned, the bactericidalsponge described above with respect to FIG. 5 maybe employed within thesealing means 154.

As the inverted flower draws water from the cavity 178, the water levelin the cavity will slowly move toward the sealing means 154 and if thelevel falls below the cut end of the stem the vascular system will drawair and the plant may wilt. Accordingly, the annulus 174 in the deviceshown in FIG. 7 provides a means to position the cut end of the stem asufficient distance from the bottom of the conduit 152 so that any airwhich enters the cavity 174, when the flower is inverted, will collectin the annular void or cavity 192 and not be drawn into the plantsvascular system. An alternative stem blocking member could be employedsuch as a perforate or sieve-like screen disposed, for example, radiallyacross the mid portion of the cavity 117 in FIG. 6. This would maintainthe cut stem at a distance from the filter end of the conduit 112 sothat a sufficient amount of liquid may be drawn into the cut flower, inan inverted position, before the liquid falls below the stem blockingmeans.

The pressurizing means shown in FIG. 8 has significant advantages,particularly with longer stemmed varietals. For example, long stemflowers including Royalty, Cara-mia and Goldenwave roses; Apple Blossomvarietal gerba; Marble varietal chrysanthemum; White Fern varietalcarnation; Leather Leaf varietal fern and Baby Breath varietaldrosophlia have endured longer than 20 days without any indication ofwilting or neck drooping.

FIG. 9 depicts novel stem support and sealing means which providessignificant advantages when employed in combination with the filtrationand pressure devices of the invention. Briefly, a novel means forsealing the stem of a plant is shown wherein a portion defining an areaadapted to receive a cut end of a stem (preferably a sterile portion)includes a layer of an initially imperforate and stem-penetrable sealingmeans such as a stem-permeable elastomer, sealed to the portion, whichis sufficiently flowable and has sufficient self-affinity or elasticityto form a seal against the inserted stem. Preferably, the elastomerforms a seal which is sufficient to resist the liquid pressure of 0.9 to1.2 psi, and most preferably forms an aseptic seal against the stem.

In FIG. 9, a support and sealing device 300 includes an essentiallycylindrical cup-shaped element 302 which is formed from a polymericmaterial such as polycarbonate or the like, although other materials maybe employed. The cup 302 includes a tapered, threaded connection nipple304 for attaching the sealing device 300 to a water source such as thereservoir 208 as is shown in FIG. 8. The cup may also be attacheddirectly to the water column or to another source of liquid pressure asdescribed above with appropriate sealing and connecting means such aswill be apparent to one of skill in the art.

As is apparent from the drawing, water or nutrient solution may flowthrough an opening 306 in the connector 304 to a water height 308 whichis determined by the water level in the attached column (as shown inFIG. 8) or the pressure which is otherwise provided on the liquidsource, e.g., gas or mechanical pressure on the liquid. Since the device300 is sealed with respect to the exit of air during the influx ofliquid through the opening 306, a hydrophobic air vent 310 is includedat the top of a lower water containing portion 312 of the cup 302 topermit the escape of air while inhibiting the influx of microorganisms,yet retain the water in the portion 312. The device is proportioned sothat the water level 308 is positioned above a lower end 314 of the stem316 which is inserted into the device 300 as hereinafter described.

The device further includes at least one layer of rigid, penetrable foam320 which is seen in the drawing to be positioned on a ledge 322. Thisfoam can be restrained in a variety of methods, for example, byadhesive, but a press fit of a slightly over-size precut foam disc intothe surrounding walls of the cup 302 will generally be sufficient. Thefoam may be hydrophilic or hydrophobic, although it is preferablyhydrophilic, and a urethane foam having a compressive strength of about5 to 18 psi such as the HP-3 foam system marketed by S. M. S andAssociates of Carlsbad, Calif. or the non-friable foam sold by thePolymer Development Laboratories, Inc. under the trade designation PDL205-1.15 are advantageous. In commercial production, this foam supportmeans can be foamed in place within the cup 302.

A layer of penetrable elastomeric sealing elastomer 330, preferablyhydrophobic, is positioned above the foam 320 and sealed against theinside of the cup 302. This material is chosen to be sufficientlyelastic to flow at about room temperature, and to rebond and seal toitself and the inserted stem 316 when the stem is inserted into thedevice 300, to form an aseptic and water-tight seal within the 0.9 to1.2 pressure range of the liquid. This self-healing consistency may beattained by employing an elastomer gel, preferably a silicone gel,having a low cross-link density, that is, a polymer with many reactivesites still available for rebonding. For example, a cross-link densityof about 40% is prefered. The elastomer preferably has a penetrabilityas measured by the ASTM D 1403 testing procedure, using a one-quarterscale cone for five seconds, of from about 13.2 mm (a limit beyond whichthe elastomer may flow into the foam or be displaced by the pressurewithin the portion 312) to about 5.5 mm (beyond which the elastomer willnot be sufficiently elastic and flowable to form a seal against theinserted stem), and most preferably about 6.0 to 7.0 mm. Generally, anRTV silicone rubber having a high self-affinity is employed, and theShin-Etsu silicone gel sold by Shin-Etsu Silicones of psi to the liquidat the cut end of the plant stem. America, Inc. under the designationKE1052A/B is preferred. This material is a transparent two-part liquidsilicone which cures into the desired flowable elastomer. As opposed toperforate seals, the initially imperforate and self-sealing elastomericseal of the invention allows the insertion of a wide variety of stemsizes and shapes in widely varied arrangements. Initially imperforate,as used herein, means that the cured elastomer forms a continuous sealacross the cup 302 prior to perforation of the elastomer by the insertedstem.

Significant advantages are provided in a sealing means which includessuspended, i.e., dispersed, particles of a water-insoluble, hydroscopicpolymer. The polymer is preferably crosslinked to provide the requiredinsolubility, and most preferably is a polyacrylamide polymer. Thepolymer particles are of a size such they are small or light enough toremain suspended in the uncured gel as the elastomer is cured, and arepresent in the elastomer in the amount of from 5 to 15 weight percent(preferably 8 to 10%) by weight of the elastomer.

The advantages of this aspect of the invention are exemplified by theuse of a water-insoluble, hydroscopic powder of a modifiedpolyacrylamide manufactured by the American Cyanamid Corporation ofWayne, N.J. under the description of Aquastore F Absorbent Polymer,which is added to the Shin-Etsu #1052 silicone.

The particulate polymer also adaptable to other sealing uses and isadvantageous in that it swells the elastomer to seal against the influxof water through or around the elastomeric seal in damp environments,and thus can be used to protect delicate electronic or other moisturesensitive components, with the insoluble nature of the polymer avoidingthe dissolving of the swollen particles over time so that the seal ismaintained.

For example, when electronic components are enclosed in protectivehousings the elastomeric sealing means of the invention may be employedin the final assembly of the housing to seal the assembled portions.e.g., in the sealing of the top against the side panels of a container.However, the hydroscopic particulate elastomer is especially useful ininstances where relatively flexible members must be sealed, for example,where members such as wires or tubes exit a sealed container through anopening which can be sealed with the elastomer of the invention. Whileexisting sealing elastomers permit the influx of small amounts ofmoisture by allowing the formation of minute passageways as the memberflexes, the hydroscopic particulates cause the elastomer to swell, toclose the passageways which would otherwise be open to the flow ofmoisture or moisture-laden air.

The dispersed particulate polymer/elastomeric seal is particularlyadvantageous as a stem sealing means in sealing leaks under the 0.9 toabout 1.2 psi pressure which is applied in the device shown in FIG. 8,thus resisting the flow of water around the stem for an extended periodof time.

A second layer of foam 332, which is similar to the layer 320 in that itmay be hydrophilic or hydrophobic and sufficiently rigid to support thestem, may optionally be placed above the elastomer 330. This foam isalso captivated within the cup, such as by a ledge 334 and a ridge 336,or by adhesive or bonding such as is described above with respect to thefoam layer 320. Preferably, a support grid is inserted into the Cup 302directly above the foam 332, the grid having openings sufficiently largeto permit the insertion of the stem Or stems 316. Such a grid willprovide additional support for the stem 316 if desired.

A layer of penetrable, self curing liquid adhesive may be applied in athin film (ca. 1 mm) over the foam 320 to inhibit leakage of the uncuredelastomer 330 into the foam during the casting process. Any thin-filmmembrane having a catalyst which is compatible with the polymerizationreaction of the elastomer 330 may be employed, although adhesives of thetype sold by Shin-Etsu Silicones of America under the trade designationKE 66 RTV are preferred. In addition, a layer of swellable, hydroscopicpulverulent material may advantageously be placed above the adhesivedescribed in this paragraph. This powdered material is preferablyhydroxyethyl cellulose of about 60 mesh (e.g., Union Carbide QP-4400HCellosize) and is sufficiently swellable to provide an additional sealagainst air and water leakage. If the adhesive and swellable powderdescribed in this paragraph are employed, the elastomer 330 may be castdirectly on the pulverulent material.

Optionally, an additional layer of swellable, hydroscopic powder mayalso be placed above the elastomer 330, e.g., at about a 6 mm thickness,to remove any water which may remain on the stem and interfere with thesealing of the elastomer. Additional advantages may also be obtainedfrom the addition, to the inner portion 312, of controlled or timerelease chemical formulations such as kinetins or other growth orpreservative factors.

According to the invention, a filtration means 340, such as has beendescribed above with respect to the other drawings, is attached acrossthe opening 306 so that the inner portion 312 receives liquid in theabsence of deleterious microorganisms and air emboli. Due to thefiltration means 340 and the seal around the stem by the sealingelastomer 330, the inner portion 312 is maintained as a sterile conduitportion. If desired, a microbicidal means such as a time releasebactericidal or fungicidal device can be advantageously attached orinserted within the portion 312.

In use, a plant stem is preferable out at about a 45 degree angle toform an insertion point as is shown in FIG. 9. The stem is then pressedinto the top layer of foam 332 of the stem support device 300. The foamparts to permit the insertion of the stem through the elastomer 330, andthereafter through the foam 320 to the inner sterile portion 312. Theelastomer flows to bond to the stem 316 and seal the inner portion 312against the influx of microorganism and the escape of liquid. The device300 is then attached to the liquid source by the nipple 304.

From the foregoing description the essential characteristics of theinvention can be readily ascertained and, without departing from thespirit and scope thereof, the invention can be adapted to varioususages. Changes in form and substitution of equivalents are contemplatedas circumstances may suggest or render expedient, and although specificterms have been employed herein, they are intended in a descriptivesense and not for purposes of limitation.

What is claimed is:
 1. A device including a reservoir and a plant stemsealing means attached thereto, the sealing means comprising aninitially imperforate, stem-penetrable elastomer which is sufficientlyflowable and has sufficient self-affinity to form a seal against aninserted stem which is sufficient to resist the flow of liquid aroundthe stem at a pressure within the reservoir of about 0.9 to about 1.2psi.
 2. The device of claim 1 in which the elastomer forms an asepticseal against the stem.
 3. The device of claim 1 or 2 in which theelastomer has a penetrability as measured by the ASTM D 1403 testingprocedure, using a one-quarter scale cone for five seconds, of fromabout 13.2 to about 5.5 mm.
 4. The device of claim 1 or 2 in which theelastomer includes suspended particles of a water-insoluble, hydroscopicpolymer.
 5. The device of claim 3 in which the elastomer includessuspended particles of a water-insoluble, hydroscopic polymer.
 6. Thedevice of claim 4 in which the polymer is present in an amount of from 5to 15 weight percent by weight of the elastomer.
 7. The device of claim5 in which the polymer is present in an amount of from 5 to 15 weightpercent by weight of the elastomer.